Magnetic deflection yoke



Aug. 21, 1962 D. BERNsTl-:IN 3,050,564

MAGNETIC DEFLECTION YoxE Filed oct. 17, 1957 2 sheets-sheet 1 HICKNE SS H IN PERCENTAGE I l l l INVENTOR: \B\ I DAGFINN BERNSTEIN, 35* l BY @Mu/7.

0 l'o 2'0" 30 4' 5'0" e'o 10 e'o 9'0 ANGULAR PLAcEMENTO( HIS ATTORNEY RELATI Aug. 21, 1962 INVENTOR- DAGFINN BERNSTEIN,

BY M521 HIS ATTORNEY.

United States Patent M 3,050,664 MAGNETIC DEFLECTION YOKE Dagiinn Bernstein, East Syracuse, N.Y., assigner to General Electric Company, a corporation of New York Filed Oct. 17, 1957, Ser. No. 690,860 5 Claims. (Cl. 317-200) This invention relates to an electron beam deflection yoke of the type suitable for use in deiiecting the electron beam of la cathode ray tube commonly used in television systems.

Heretofore, saddle-type deflection yokes have been designed to have either a high or a low impedance. Generally, the impedance of the yoke is selected in the same order of magnitude as the impedance of a source of deflection energy. Often it is necessary to use `a matching transformer to provide a suitably impedance match. If devices having inherently lower impedances, such as transistors, `are used to control the deflection energy, the yoke which is to be driven by such energy must have an exceedingly low impedance, otherwise a transformer or other matching means must be inserted between the transistor and the yoke.

Accordingly, it is an object of this invention to provide a new and improved deilection yoke having -an impedance such that it may be directly driven from a low impedance source without providing a matching transformer or other types of matching devices.

Low impedance yokes generally have fewer turns of large diameter single wire or multi-strand wire. Various turn distributions having gradual changes in coil thickness have been used to produce properly shaped deectio-n elds, for example, the cosine type distribution. However, with relatively large diameter wire it becomes exceedingly difficult to wind yoke coils having such distribution.

Consequently, another object of this invention is to provide a new and improved deilection yoke which may be manufactured from large diameter wire with a suitable distribution.

It is generally recognized that the eiciency and other operational characteristics of magnetic deflection yokes are. improved if as much wire `as possible is concentrated in the volume between the customary core and the neck of the cathode ray tube.

n Accordingly, 'another object of this invention is to provide a new and improved magnetic deflection yoke in which all of the volume between the neck of a cathode ray tube and the core is lilled with turns of wire.

4 .As is well known in the art, it is essential that the respective magnetic fields provided by the horizontal and vertical deection coils be mutually perpendicular. Prior art coils have configurations that give no indication of the proper relative posit-ions ncessary for accurate `alignment. In fact most distributions make it impossible. Consequently, accurate alignment is achieved by adjusting the relative coil positions until a desired end result -is obtained.

` Therefore, another object of this invention is to prov-ide -a new `and improved ydeflection yoke having a winding distribution such that when the coils are interitted, they are properly orientated to provide mutually perpendicular ields without ladditional alignment or adjustment means.

" With the turn distribution used in prior art yokes, some means, usually called la coil form, is generally required to aid in holding the coils in position of approximately correct alignment.

Inasmuch as the coil form always occupies space that could be lled with wire, if maximum efficiency is to be obtained, it is another object of this invention to provide a yoke having a turn distribution that requires no coil forms. i

3,050,664 Patented Aug. 21, 1962 ICC As is well understood by those skilled -in the art, these coil forms are also used for the purpose of providing insulation between the various coils. In certain types of yokes, e.g. low impedance yokes, insulation between the coils is not necessary, but, as previously pointed out, it is still necessary for alignment purposes in prior art yokes. The yoke of this invention makes it possible to entirely eliminate the coil forms in these types of yokes.

Still a further object of this invention is to provide a new and improved defiection yoke for cathode ray tubes and like devices which is economical and easy to construct.

In carrying out this invention in one illustrative form thereof, an electron beam deflection yoke is provided having a first and second pair of coils. Each of said coils consists of a pair of coil sides having at least a portion adapted to extend lengthwise along the surface of the neck portion of a cathode ray tube, and each is terminated in curved end portions, thereby forming a saddletype configuration. Each coil side is stepped or L-shaped and is adapted for interlocking registration with a similar but inverted stepped or L-shaped coil side of -another coil. When constructed and arranged in accordance with this invention, the coils cooperate to form an `annulus of turns having a cylindrical opening which is adapted to accommodate the neck of a cathode ray tube.

These and other advantages of this invention will be more clearly understood from the following description taken in connection with the accompanying drawings, and its scope will be apparent from the appended claims.

In the drawings:

FIG. l is -a perspective view of the deflection yoke embodied in this invention;

FIG. 2 is a cross-sectional view taken along lines 2 2 of FIG. l;

FIG. 3 is -an exploded perspective View of the yoke shown in FIG. l; and

FIG. 4 shows a series of curves representing various yoke coil distributions including the distribution embodied in this invention.

Referring now to FIGS. 1 and 3, the magnetic deflection yoke, designated generally by the reference character 10, includes two diametnically opposed horizontal deecting coils 111 and 17 having coil sides 13 and 15, and 19 and 21, respectively. Yoke 10 also includes two diametrically opposed vertical'deecting coi-ls 23 and 29'` having coil sides 25 and '27, and 31 `and 33, respectively.

As is best seen in FIG. 2, the horizontal and vertical deflecting coils are saddle-shaped. 'Ilheir respective coil sides are intertted so as to form a substantially complete hollow cylinder 30 with their outwardly bent ends overlying each other and being flared on one end thereof to accommodate the flared funnel of a cathode ray tube as shown in FIG. 1. Whereas FIGS. 1 and 3 show an embodiment of this invention having a cylindrical section as well as a ilared or conical section, it will readily be understood that the invention may have application to a deflection yoke that is essentially cylindrical. Magnetic yoke 10 when energized is adapted to deflect a cathode ray beam in two mutually perpendicular transverse planes through the tube axis 50.

For a better understanding of the arrangement and construction of the coils to form yoke 10, reference is now made to FIG. 2. Coil sides 13 and 15 of coil 11 are generally L-shaped or step-like in cross-sectional dimension thereby providing a radial step-wise change in thickness along the coil 11 with respect to the coil axis 50. Similar L-shaped or step-like construction is provided in coil sides 19 and 21 of coil 17. Coil 23 has L-shaped sides 25 and 27 which are inverted and are complementary to the L-shaped sides 13 and 21, respectively. Similarly, coil 29 has L-shaped sides 31 and 33 which are inverted and are complementary with respect to the L-shaped sides and 19, respectively.

As will appear obvious in FIG. 2 the complementary L-shaped or stepped construction yof coil sides 115 and 311 are adapted for interlocking registration. The same is true with respect to coil sides 25 and 13; 21 and 27; `and 33 and 19. The coils when so interlocked form an annulus of turns of wire around the axis 50 providing an opening 30 therein adapted to receive the neck of a cathode ray tube. A cooperating magnetic core (not shown) is adapted to t over the annulus of turns so formed.

For a better understanding of the invention, reference is now made to FIG. 4 which shows several curves of the relative coil thickness versus the angular displacement thereby representing various yoke coi-l distributions about the neck of a cathode ray tube. Curve I represents a pure cosine coil distribution which would theoretically create a uniform magnetic field. This would not necessarily be desired due to cathode ray tube geometry, etc. Because television systems require deflection in both the horizontal and vertical planes, two adjacent pairs of coils cannot both have pure cosine distributions and still fit together to utilize the greatest amount of space available between a yoke core and the neck of a cathode ray tube. If two similar coils are to be interiitted in a quadrant in such fashion as to leave no space between them and provide a uniform thickness of wire throughout the quadrant, that is necessarily equal to the maximum thickness of the coils, each coil at the mid point of the quadrant, or at 45 degrees, must be approximately half as thick as the maximum thickness. An examination of curve I of FIG. 4 shows that this is impossible for a pure cosine distribution inasasmuch as such a distribution has a thickness at 45 degrees or at the mid-point that is equal to 70.7% of the maximum thickness.

Curve II represents a more practical yoke distribution which is an approximation of the pure cosine distribution of curve I. 'llhis type of distribution has been employed in a number of currently used deflection yokes. At the mid-point or at an angle of 45 degrees, the thickness of the coil is approximately 50% of the maximum thickness. Consequently, two coils having a distribution approximately such as illustrated by curve II may be interfitted in one quadrant without leaving much space between them. By such a configuration, more of the available space between the tube and the core in any one given quadrant is occupied.

However, even the distribution illustrated by curve II does not ll all of the space between the neck of the tube and the core. It is obvious that the minimum thickness of a coil cannot be less than the diameter of one turn of wire as illustrated by the vertical portion 35 of the curve II. Hence there is no more Wire from this point to 90 degrees and a wasted space is present.

Curve III shows the step-type distribution of this invention in which the desired magnetic eld is approximated just as well as with `the coil distribution shown on curve II. With the step-type distribution, however, all the available space in any given quadrant is lled with windings for the reason that another coil having a distribution as represented by the vertical line A, the horizontal line 41 and the vertical line B of curve III and the dotted line 39 is complementary to the coil represented by the curve III. It is not necessary for the steps A and B to be perfectly straight. They may be slanted as indicated by lines C and D as shown on curve III to provide for easier winding.

Steps A and B may be shifted left or right to provide variations of the distribution shown by curve III. However, changing the steps (position of lines A and B) will vary the raster shape and spot size. For example, if the steps A and B are moved closer together picture quality will deteriorate. If the steps A and B are moved further apart, Winding diiculties arise. Consequently, the type 4 of `distribution shown on curve -III represents a compromise between both the `winding and electrical considerations.

Other variations in the distribution represented by curve III are possible. For example, the horizontal section 41 could be moved up or down, and if the available space is still filled with wire, the result is to transfer wire from one coil to the other. As will readily be understood by those skilled in the art, this yproduces changes in the Q of the coils as well as in the shape of the deection elds and hence in the shape of the scanned raster. It should also be noted that more than the two steps shown on curve III may be provided. However, for each additional step, practical winding difficulties increase.

ln the specific embodiments of the invention discussed, the description of the distribution of the coil windings has been principally directed to the cylindrical section. Whereas this distribution could be applied to the flared portion of the yoke, it is not essential, as the design consideration for this portion of the yoke are essentially the Isame as in previous yokes. Obviously, however, the different distribution employed in the cylindrical portion of a yoke of this invention will require that the wires be flared into the conical section in a slightly different manner than in previous yokes.

As has been explained, all of the space available between core and the neck portion of a cathode ray tube is completely filled with turns of wire. Such a concentration of conductors, provides better yoke eiciency. As was also explained, the overlapping of the horizontal and vertical coils by this interfitting complementary step or L-shaped construction provides an approximation of the 'most suitable type of distribution to provide the desired magnetic elds and thus reduce distortions in the picture on the cat-hode ray tube screen.

One advantageous feature of the Istep-type distribution allows the coils of the yoke to be conventionally wound with a single strand of wire having larger diameters than the other types of distribution. The coils may also be 'wound with layers or bundles of multi-strand wire to increase the effective wire diameter and -to reduce A.C. resistance-(skin effect, proximity effect, etc.). -For example, from the coil distribution shown in curve II, the largest possible diameter wire which may be used corresponds to Ithe length of line 35. It can be readily seen that the distribution shown in curve III provides a greater latitude in the diameter of Wire which may be used inasmuch as the wire diameter could be equal to the length of the line B or a submultiple thereof. This is particularly important with respect to the winding of the horizontal deiiection coils. When energizing the horizontal deection coils from a transistorized horizontal deflection driving stage, it is essential that the horizontal deliection coils have a low impedance to permit direct drive. Otherwise, a matching transformer would be required between the horizontal drive stage and the horizontal deflection coils. In accordance with the present invention the horizontal deflection coils may be wound with plural stranded wire or with larger diameter wire to substantially reduce the coil impedance, and thus eliminate the need for a matching transformer.

When the yoke 10 embodied in this invention is used with low sweep voltages, such as those employed in transistorized deflection circuits, no coil forms or spacers or insulation other than the ordinary insulation applied to the coil wire is necessary. Consequently, the space ordinarily occupied by such coil forms or spacers is occupied with turns of wire giving greater yoke eticiency than available from structure-s using such forms. As will be obvious to those skilled in the art, insulation may be provided bet-Ween the L-shaped coil sides adapting the present yoke to be used as a higher impedance device or with higher sweep voltages. Even in this case, it will be apparent that the -space available still is more fully utilized for turns of wire than would be available in prior art disclosures.

As will be apparent to those skilled in the art, it is essential that the magnetic fields of the horizontal and vertical deflecting coils be mutually perpendicular in order that no cross-talk interference exist. In many prior art disclosures, it has been necessary to align the vertical and horizontal coils to provide mutually perpendicular fields. For example, this might be done by proper alignment during assembly. However, with the present invention the coils are so constructed and arranged that when they are assembled no further adjustments are necessary. The coils are properly aligned when assembled thereby eliminating the needless expense of alignment means.

As has been previously explained, the winding operations for coils embodied in this invent-ion has been simplified. The coils may be readily wound with conventional saddle-type coil winding machines and inserts. The inserts are tools used to wind the coils on. These inserts are easy to manufacture because of their circular symmetry, which cosine type distribution inserts do not have.

In the foregoing description of the yoke 10, longer coils 11 and 417 are described as the horizontal deflection coils. This is a preferred construction due to the higher eiiiciency of the longer coils which is more necessary in the horizontal deflection circuits. However, shorter coils 23 and Z9 may be used to provide horizontal deection if desired.

Since other modifications varied to fit particular operating requirements and environments will be apparent to those skilled in the art, the invention is not considered limited to the examples chosen for purposes of disclosure and covers all changes and modifications which do not constitute departures from the true spirit and scope of this invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. An electron beam deflection yoke comprising a rst and a second pair of transverse deflection coils, each coil having a pair of coil sides with sections thereof extending lengthwise along the longitudinal axis of said yoke and parallel thereto, each coil being terminated in curved end portions, each of said sections having a generally L- shaped cross-section in a plane perpendicular to the longitudinal axis of said yoke for registration with at least another of said deflection coils for interlocking said coils around the longitudinal axis of said yoke to form an opening about said axis.

2. A magnetic deflection yoke for producing a deflecting ield for the deflection of a cathode ray beam in a cathode ray tube comprising a pair of horizontal deflection coils, each coil having a pair of curved coil sides with sections thereof extending lengthwise along the longitudinal axis of said yoke and parallel thereto, and each coil being terminated in curved end portions to form a saddle-like conliguration, each of said sections having a generally L-shaped cross-section in a plane perpendicular to the longitudinal axis of said yoke, a pair of vertical deilection coils, each coil having a pair of curved coil sides with sections thereof extending lengthwise along the longitudinal axis of said yoke Iand parallel thereto, and each coil being terminated in curved end portions to form a saddle-like configuration, each of said last-named sections having a generally L-shaped cross-section in a plane perpendicular to the longitudinal axis of said yoke for interlocking registration with the generally L-shaped cross-sections of said coil sides of said horizontal deliection coils -to form Ia cylindrically shaped opening.

3. An electron beam deflection yoke comprising a plurality of coils longitudinally disposed with reference to the axis of said yoke and distributed around said axis so as to define a cylindrical space within said yoke, each of said coils having coil sides with sections thereof extending lengthwise along the longitudinal axis of said yoke and parallel thereto, each of said sections having a generally L-shaped cross-section in a plane perpendicular to the longitudinal axis of said yoke and longitudinally overlapping at least another one of said sections to form an annulus of coils around said cylindrical space having substantially uniform radial thickness around said axis.

4. A coil assembly comprising a plurality of coils each having sides and ends and window openings defined by said sides and ends, sections of each of said sides being substantially parallel and together defining an annulus around a cylinder having an axis substantially parallel to the sections iof said sides, each of said sections having a generally L-shaped cross-section in a plane perpendicular to the axis for registration with a complementary section of an adjacent coil side for providing an annulus of coil `windings about said cylinder having substantially a uniform radial thickness.

5. A magnetic yoke comprising first, second, third and fourth coils each having sides and ends and window openings deiined by said sides and ends, sections of each of said sides extending lengthwise along the longitudinal axis of said yoke and parallel thereto, each of said sections having a generally L-shaped cross-section in a plane perpendicular to the longitudinal axis of said yoke, said sections of said first and said second coils registering with complementary sections of said third and said fourth coils to define a cylindrical opening surrounded by an annulus of coils having a substantially uniform radial thickness about the axis of said cylindrical opening.

References Cited in the file of this patent UNITED STATES PATENTS 2,148,398 Bowman-Manifold et al. Feb. 2l, 1939 2,565,331 Torsch Aug. 21, 1951 2,570,425 Bocciarelli Oct. 9, 1951 2,831,997 Marley Apr. 22, 1958 2,899,578 Kirkham et al Aug. l1, 1959 2,955,220 Snyder Oct. 4, 1960 2,986,667 Tirico May 30, 1961 FOREIGN PATENTS 1,123,480 France June 11, 1956 791,039 Great Britain Feb. 19, 1958 

